Nondestructive inspection with a radiation ray is widely conducted in industries, medical treatments, and so forth.
An X-ray, for example as a kind of the radiation rays, is an electromagnetic ray having a wavelength in the range from about 0.01 Å to 10 nm (1012 to 108 m). The X-ray having a shorter wavelength (about 2 keV or higher) is called a hard X-ray, and the X-rays having a longer wavelength (about 0.1 keV to about 2 keV) is called a soft X-ray.
The X-ray absorption contrast method is employed practically, for example, for inspection of an internal crack in iron and steel or baggage security inspection by utilizing the difference in the absorptive power of the highly penetrative X-ray.
On the other hand, for detection of an object having a less difference in the density from the surrounding medium and causing less contrast of X-ray absorption, an X-ray phase contrast imaging method is effective which detects phase shift of the X-ray by the object. Such an X-ray phase contrast imaging method is being studied for imaging of polymer blends and to medical treatment, and so forth.
Of various X-ray phase contrast imaging methods, the refraction contrast method disclosed in Patent Document 1 below utilizes a refraction effect resulting from the phase shift caused by an object.
This refraction contrast method picks up an image by a fine focus X-ray source with a detector placed at a large distance from the object. This refraction contrast method obtains the edge-enhanced image of the object by the X-ray refraction effect by the object.
Further, this refraction contrast method, which utilizes the refraction effect, does not necessarily require a highly coherent X-ray like a synchrotron radiation, which is different from usual X-ray imaging method.
On the other hand, Patent Document 2 discloses an imaging apparatus which has a mask to shield an X-ray at the edge portions of the pixels of the detector. By placing the mask to be irradiated partly by an X-ray in the absence of an object, a shift of the position of the X-ray caused by the refraction effect of the object can be detected as an intensity change of the X-ray.
[Prior Art Documents]
[Patent Documents]
    [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-102215    [Patent Document 2] International Patent Application Laid-Open No. 2008/029107